1. Field of Invention
The present invention is generally related to waste collection devices, system, and methods. In particular, the present invention is related to a primary waste collection unit operation that mechanically filters or screens natural surface water systems, including rivers, lakes, and oceans, to collect, for further handling and treatment, solid waste materials contained in those water systems using the movement of the water as an energy source.
2. Description of the Related Art
It is not uncommon to find solid waste accumulating in streams, rivers, lakes, harbors, bays, beaches and oceans due to anthropogenic activities. That solid waste is not only unsightly and potentially odiferous, but it potentially causes adverse environmental and human health impacts if it is not removed from the environment and disposed of in a proper manner.
One technique for remediating solid waste in relatively calm and navigable surface waters, such as harbors, lakes, and rivers, was developed in the 1980's by New York City's Department of Sanitation (DSNY), and involves a floating, self-contained, self-propelled, conveyorized trash skimmer, commercially available today under the name TRASHCAT™, which is available from United Marine Technologies. Also called a “skimmer boat,” a TRASHCAT™ is a catamaran-like, twin-hull vessel on which are mounted hydraulically powered and controlled open mesh conveyor systems to collect solid waste from surface waters. One end of the inclined continuous conveyor is adapted to being lowered into the water and, when operated, skims floating debris off the surface of the water to depths of up to 2½ feet below the surface. The vessel is optionally equipped with conveyorized skimming “wings” mounted on each side of the main conveyor that extend outward away from the vessel at angles to form a funnel that allows the vessel to maneuver and skim a 16-foot wide area. A diesel engine is used to power a hydraulic pump and other mechanical devices on the vessel, as well as to operate one or more propulsion propellers. According to the literature associated with the TRASHCAT™ skimmer vessel, solid waste transported up the main pickup conveyor is dumped into a storage area on the vessel, which, with its sidewalls, is adapted to hold up to 12,000 pounds or 700 cubic feet of solid waste skimmed from the water on which the vessel operates.
Solid waste collection “skimmer boats,” like the TRASHCAT™, and related components are described in several patent references, including U.S. Pat. No. 3,268,081 (describing a floating skimmer boat without a conveyor); U.S. Pat. No. 3,539,048 (describing a basic skimmer boat conveyor system for collecting flotsam from water surfaces); U.S. Pat. No. 3,968,041 (describing a skimmer vessel that can be fixed in place relative to a moving plume of oil for skimming the oil); U.S. Pat. No. 4,322,294 (describing a skimmer boat with a height-adjustable conveyor component); U.S. Pat. No. 5,028,325 (describing a skimmer vessel with a conveyor with one-eight-inch spaced plastic-coated wires adapted to collecting cigarette butts, among other debris common in waterways); and U.S. Pat. No. 7,045,058 (describing a vessel whereby the conveyor operates in both directions for skimming and then discharging the collected solid waste).
Similar screening techniques, but used primarily for removing solid waste from municipal networked piped systems, such as those associated with municipal wastewater treatment facilities, have also been known for many years. One such technique uses a rotary conveyor or drum screen placed in the path of the wastewater to intercept course solids in the wastewater as described and depicted in Metcalf & Eddy, Inc., Wastewater Engineering: Treatment, Disposal and Reuse, 3d ed., McGraw-Hill (1991) at 452. A rotary conveyor or drum screen consists of an influent pipe that conveys wastewater, a rotary conveyor or drum screen partially submerged in the influent water, and a series of effluent pipes that convey the screened wastewater to downstream unit operations for further treatment. The key to the rotary screening unit operation is a rotary conveyor or drum that is fitted with a skin of slotted or perforated openings that allows water to pass through but which collects course solids entrained in the wastewater. As the conveyor or drum rotates, it lifts waste material out of the water and, as it rotates about a central shaft, causes the waste material or “screenings” to fall off of the screens and into collection devices. The rotary conveyor or drum is typically powered by an electrical motor attached to a pulley that loops around a gear on the rotary conveyor drum shaft, or it may be hydraulically operated.
Hence, heretofore, techniques for screening solid waste that have accumulated in surface waters have generally required using a motorized boat that is adapted to maneuvering through the contaminated water to retrieve the solid waste, whereas techniques for screening solid waste that are present in piped wastewater systems have involved in-line, electrically- or hydraulically-powered rotary conveyor or drum systems (among other mechanical techniques not described). Neither system, however, is adapted to operate in relatively turbulent and potentially non-navigable surface waters such as swift rivers that traverse large, populated watersheds, such as the Chesapeake Bay watershed located in the Mid-Atlantic region. Hence, the need for such a system exists.
One advantage of using screening techniques in upstream locations away from harbors and bays, where much of the solid waste eventually accumulates, is that the amount of solid waste making it to those locations is reduced. However, a disadvantage of operating screening devices at such remote locations is that power required to operate the equipment may not be available, or it may be intermittent. One solution to that problem is to use a paddle wheel as generally described in U.S. Pat. No. 5,136,174 (describing a series of paddle wheels placed in the direction of flowing water to generate electricity). Other electrical generating methods, including wind and solar power generators, have been described in other patent references.